The invention is related to detecting and predicting ovulation and/or a period of fertility in a female mammal, such as a female human. Knowledge about ovulation and/or the period of fertility allows family planning in the form of avoiding pregnancy, e.g. by practising sexual abstinence or other forms of birth control during the period of fertility. Alternatively, if so desired, the probability of conceiving can be increased by practicing sexual intercourse during the female fertile period.
Ovulation and/or the period of fertility of a female can be predicted using a method referred to as natural family planning (NFP) sympto thermal method (STM). NFP/STM is a fertility awareness based (FAB) prediction method which uses as indicators for fertility a body temperature and a property of cervical mucus. NFP/STM is known in the art and will not be explained in detail here.
The average body temperature of a female human is known to change during the menstrual cycle. Commonly, the average body temperature rises by at least 0.2° C. after ovulation. Hence, monitoring the body temperature over time gives an indication of the fertility of the female.
The cervical mucus is also known to change during the menstrual cycle. During the immediate pre-ovulatory phase, for a period of one to three days, the cervical mucus is profuse and watery; the cervical mucus is most hydrated (97 to 98% water) at the time of ovulation. At other times of the menstrual cycle, the cervical mucus is less abundant, relatively dehydrated (80 to 90% water) and no longer possesses certain threadability characteristics, or in rheological terms is more viscous. Also, the cervical mucus is normally cloudy, but becomes transparent three to four days before ovulation.
It is known in the art to predict ovulation and/or the period of fertility based on body temperature and a property of the cervical mucus. One known method determines the optical transparency of the cervical mucus. It has been found, however, that determining a rheological property of the mucus allows for more accurate prediction of ovulation and/or the period of fertility.
It is known to determine a threadability of the cervical mucus by hand, by threading the mucus between the thumb and a finger by gradually increasing the distance between the thumb and the finger, e.g. until the thread of mucus breaks. This method is, however, generally regarded as messy.
Several methods and devices are known for determining a rheological property of a bodily mucus, more in particular cervical mucus for determining the phase of the menstrual cycle.
American patent specification U.S. Pat. No. 3,982,423 discloses a testing process and device wherein a sample of mucus is inserted in a thin ring shaped cavity between an inner and outer member. One member is mounted stationary, the other member is weighted to move relative to the first mentioned member when the viscosity of the mucus is relatively low and not to move when the viscosity of the mucus is relatively high. This device has the disadvantage that it gives no indication of how high the viscosity of the mucus is, but only an indication whether or not the viscosity is above or below a predetermined threshold value.
Spanish patent specification ES 2 031 038 discloses a device in the form of tweezers, wherein a sample of mucus is placed between the tips of the two legs of the tweezers. The legs are moved away from each other until a thread of mucus formed between the tips breaks. The device is provided with a scale for determining the maximum length of the thread just prior to breaking. This device has the disadvantage that the length of the thread as determined from the scale may depend largely on the skill of an operator of the device to read the scale and to maintain the legs in the relative position in which the thread broke after breaking until the scale has been read.
Further, these devices and methods have the disadvantage that they are not user-friendly and require some skill to be operated. Hence, these devices and methods are not suitable to be used by untrained persons. Especially in predicting ovulation and/or the period of fertility in women, it is strongly desirable that a woman can operate the device and/or practice the method herself, e.g. in the comfort of her own home.